The manufacture of annular tread belts for later assembly to an unvulcanized tire carcass is known.
One method described in U.S. Pat. No. 3,865,670 taught the use of an expansible and contractible transfer ring for conveying a breaker tread assembly from a building drum in a tire building machine to a tire carcass mounted on a tire shaping machine.
An improved but somewhat similar U.S. Pat. No. 3,888,720 also disclosed a separate tread breaker building drum designed to vary in size to accommodate different sizes of tires.
Similarly, the Charles E. Todd U.S. Pat. No. 3,865,669 also disclosed an expansible and contractible transfer ring for conveying a breaker-tread assembly.
Each of these prior art patents recognized that an assembly of a tread belt to a tire carcass can be accomplished off-line or separate from the carcass building machine. Once formed into a ring these tread breaker assemblies could be moved to encircle a tire carcass, the carcass inflated to contact the inner surface of the tread breaker assembly and then stitched together by a roller mechanism to form a green or uncured tire assembly to be placed into a mold.
While these assembly techniques provided efficiencies in production, none really changed the method for actually forming a tire assembly.
Conventional tire molds, whether two piece molds or segmented molds, form the tread surfaces by pressing groove forming ribs and sipe forming blades into the tread rubber as the tire is molded. As this is done the belt cords, particularly those directly under the groove-forming ribs deflect in small but noticeable undulations. These undulations create a variety of changes across the tread that actually can vary the surface or change the amount of tread rubber across the otherwise normal appearing tire. These non-uniformities can lead to mass imbalance issues, irregular wear and a variety of associated ride and handling performance issues. The goal in tire manufacturing is to minimize unpredictable non-uniformities in manufacturing while also building the tire in a very cost-efficient manner.
In the manufacture of very large tires the curing cycle my take many hours. A faster way to build such large tires is to form the tread belt assembly and the carcass assembly separately and to separately vulcanize these assemblies to create a two piece tire system. The separate curing of the tread belt structure and the carcass structure can save several hours of curing tires. Furthermore, the carcass assembly can survive several tread belt lives so the end product is much more efficient in its use. Four to five tread belts can used on a single carcass. This means the manufacturer must build several times more tread belts than carcass assemblies. A typical two piece tire assembly is described in Rayman U.S. Pat. No. 6,561,241 issued May 13, 2003.
In U.S. Pat. No. 6,526,659, a method of changing very large tires is disclosed. In that patent it is noted that tread belt pneumatic tires which are subject to the method of the present invention are very large tires (greater than 119.9 inches outside diameter (OD)) generally designed for use on very large vehicles, generally off-the-road vehicles such as earthmovers and large capacity mining trucks (e.g., 300 short tons or more). The size of these tires is extremely large. For an example, the tire weight can be approximately 8,000 pounds (3,628 kg) to 15,000 pounds (6,803 kg) or more for an unmounted tire. When using a two-piece type tire wherein the tread belt forms the outer structure and the inner structure is formed by a carcass wherein the two parts are separable, the tread belt alone will weigh over 4,000 pounds typically, many times more depending on the size. By way of example, a 57 inch nominal rim diameter two-piece tire having a 45R57 size will have a tread belt assembly having an outside diameter of approximately 12 foot or roughly 144 inches and will weigh approximately a little more than 4,500 pounds, a smaller but still very large 51 inch nominal rim diameter tire of a 3300R51 size yields a 3000 lb. tread belt, and the massive 63 inch 59R63 tire has a tread belt weighing in at 8424 lbs.
Slight variations in the manufacturing process can be very costly. A one-percent variation in material can cause a 30 to 85 pound weight change. In the manufacture of small tires a two percent variation is quite common.
It is an object of the present invention to provide a tread belt assembly method that very precisely applies the components and can control the application to minimize weight variations.
It is a further object of the invention to provide a portable collapsible building drum apparatus that can be easily and quickly moved from a building station to a transfer station and back.